QTL clustering as a mechanism for rapid multi-trait evolution

Cave-dwelling animals exhibit remarkable convergence in multiple cave-related traits, yet the genetic mechanisms responsible for the evolution and integration of many such traits remain unclear. Astyanax mexicanus is a model cave-dwelling fish with sighted surface-dwelling (surface fish) and blind cave-dwelling (cavefish) forms. Using a genetic cross between these morphs, we discovered significant correlations among several cave-related traits, including reduced eyes, increased superficial neuromast receptors located within the eye orbit (EO SN) and a vibration-attraction behavior (VAB) that facilitates foraging in darkness. Furthermore, we discovered that the quantitative trait loci (QTL) underlying these traits are clustered within the Astyanax genome. Following an ablation experiment that demonstrated that the EO SN contribute to VAB, we concluded that the adaptive evolution of VAB and EO SN has likely contributed to eye loss in cavefish. In this addendum, we further discuss the possible role of multi-trait QTL clustering in facilitating rapid adaptation.